Characterization of Absorptivities To Solar Radiation for Colored Pigments in Coatings

By Hong-You Guo, Xiu-Yan Li, Ping Wang

Colored pigments absorptivities to solar radiation have been characterized quantitatively by measuring the absorption coefficients of the colored pigments mixed in white titanium dioxide standard coating. The standard coating contains white TiO2 with 17% pigment volume concentration (PVC).

Dry white coating with more than 134 µm thickness is opaque and used as a dispersion medium for colored pigments. The reflectances of the coatings of white TiO2 and three kinds of colored pigments (perylene black, toluidine red, and benzidine yellow) to solar radiation are measured by means of a UV-3100 recording spectrophotometer operating in the 250~2500 nm spectral range.

It is found that the plots of lg 1/R (R, reflectance of coating to solar radiation) against (volume ratio of the colored pigment to TiO2 in coating) are straight lines of increasing slopes in the range of less than five percent. From the slopes of the straight lines, the absorption coefficients of colored pigments can be measured quantitatively.